Not enough...
As a recent convert to the Blade "hype", aside from their "proprietary nature" I personally believe they are the biggest leap forward yet in the server market and as such I will never regret the decision.
We invited IBM, HP and DELL to kit us out, but at the end of the day only IBM could meet our requirements - the reason? simply the networking flexibility, IBM offers a vast array of different switches.
Until Dell address this aspect of their chassis, they're are losing out.